Yes. As the deputy said, we've used these 20-year estimates for air programs since 2004. There is a significant amount of uncertainty in aerospace technology costs when you get beyond the 20 years. It becomes very difficult to predict. We have 60 years of experience in flying jet fighters, and we understand how difficult it is to predict those technical and structural issues.
For example, when we introduced the CF-18, we experienced structural issues with the vertical stabilizers. This was totally unpredictable, and we had to resolve those issues.
Over the past seven years we've tried to put in place performance-based, long-term support contracts for our air fleets, like the new Hercules CC-130J fleets. Industry came back to us and told us they could not agree to long-term rates without imposing large price increases to mitigate the uncertainty of future costs. We ended up negotiating 20-year contracts based on firm fixed rates for only five years at a time.